This invention relates to a process for curing liquid isocyanate-terminated polyurethane prepolymers by mixing them with 10% to 200% by weight, based on the weight of the prepolymer, of an aqueous dispersion or solution of an organic hydroxy silicate compound and their condensation products. This novel organic hydroxy silicate and their condensation products are effective both as a curing agents and as a low cost extender for polyurethane prepolymers. The products cured by this method may be quite varied in physical properties; they may be solid or porous, rigid or elastomeric, and the porous products may be rigid or soft and flexible.
The products produced by curing liquid isocyanate-terminated polyurethane prepolymer may be utilized as thermal insulating material, noise insulating material, shock-resistant packaging, cushions, as coating agents, as adehesives, as casting material, as constructional components of a building, etc.
The products have improved heat and flame resistant properties.
The organic hydroxy silicate compound and their condensation products utilized in this process may be produced by the process of the Claims and Examples in U.S. patent application Ser. No. 765,050, filed on Feb. 2, 1977, by David H. Blount. Details of the process to produce silicon acids, hydrated silica and silicoformic acid, and the process to produce organic hydroxy silicate compounds and their condensation products may be found in that U.S. patent application. The Infrared KBr Analysis of both the silicon acids and organic hydroxy silicate compounds were included in my U.S. patent application Ser. No. 765,050.
In U.S. patent application Ser. No. 663,924, filed on March 4, 1976, and U.S. patent application Ser. No. 599,000, filed on July 7, 1975, by David H. Blount, the silicon acids are reacted with polyisocyanate compounds, but not with liquid isocyanate-terminated polyurethane prepolymers. In U.S. Pat. Nos. 3,981,831; 3,975,316 and German Pat. No. 2,325,090, an aqueous silica sol and silicates were utilized in their process, but they did not utilize organic hydroxy silicate compounds and their condensation products to produce polyurethane products.
The silicon acids, hydrated silica and hydrated silica containing Si-H bonds may be produced by any of the commonly known methods. They are preferred to be in a fine granular form.
The silicon acids will react chemically with monohydroxy and polyhydroxy organic compounds to produce organic hydroxy silicate compounds and their condensation products. These novel organic hydroxy silicate compounds and condensation products will react chemically with isocyanates, organic acids, polycarboxylic acids and anhydrides and epoxy compounds.
The organic hydroxy silicate compounds and their condensation products are produced by chemically reacting a silicon acid, such as hydrated silica and hydrated silica containing Si-H groups with an organic hydroxy compound, by heating the mixture in the presence of an alkali catalyst to a temperature just below the boiling temperature of the organic hydroxyl compound while agitating for 20 to 60 minutes at ambient pressure, thereby producing organic hydroxy silicate compounds and their condensation products.
Various alkali compounds such as alkali metal carbonates, hydroxides, oxides and alkali metal salts of weak acids may be used as the alkali catalyst in the chemical reaction to produce organic hydroxy silicate compounds and their condensation products. The preferred alkali compound is sodium carbonate. Other useful alkali compounds are potassium carbonate, sodium hydroxide, potassium hydroxide and sodium silicate. Best results are obtained when the alkali catalyst is added in the amount of 1% to 10% of the weight of the reactants, hydrated silica and organic hydroxyl compound. The alkali catalyst is necessary in this process because when an organic hydroxyl compound is heated with hydrated silica without an alkali catalyst, no organic hydroxy silicate compound is produced. It is possible to produce a colloidal dispersion of silica hydrogel in polyols when a silica hydrogel is heated in a polyol while agitating without the presence of an alkali catalyst, but not an organic hydroxy silicate compound. Infrared analysis of a colloidal dispersion of silica hydrogen in polyols shows that the polyol does not react with the silica.
Various monohydroxy compounds may be used in this process to to produce organic hydroxyl silicate compounds such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, amyl, hexyl, octyl, benzyl and allyl alcohols and thioalcohols, phenols, cresols, thiophenols, cyclohexanol, methylcyclohexanol, cyclohexano-methanol, methallyl alcohol thiocresols, halogenated alcohols and mixtures thereof.
Various polyhydroxyl compounds may be used in this process to produce organic hydroxyl silicate compounds and their condensation products such as glycerol, glycerol monochlorohydrin, ethylene glycol, propylene glycol, butylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, tetraethylene glycol, polyethylene glycols, ether glycols, Bisphenol A, resorcinol bis (beta-hydroxyethyl) terephthalate, 2-ethyl-2-(hydroxymethyl)-1,3-propanediol, pentaerythritol, trimethol propane, trimethol ethane, 2,2-oxydiethanol, glucose, mannose, fructose, molasses, cane sugar, dextrines, starches, corn syrup, maple syrup, castor oil and mixtures thereof.
Various organic compounds containing hydroxyl radicals may be used to produce organic hydroxy silicate compounds such as glycolic acid, malic acid, 10 hydroxy undecanoic acid, 2-hydroxy decanoic acid, 10 hydroxy pentadecanoic acid, monoglycerides of fatty acids, halogenated alcohols, etc. and mixtures thereof.
One part by weight of an organic hydroxyl silicate compound and polymer, containing 0 to 1 part by weight of water may be reacted with 0.5 to 6 parts by weight of a liquid isocyanate-terminated polyurethane prepolymer to produce a solid/solid fine cellular polyurethane product.
Any suitable polyisocyanate may be used to produce the liquid isocyanate-terminated polyurethane prepolymer, for example, arylene polyisocyanates such as tolylene, metaphenylene, 4-chlorophenylene-1,3-, methylene-bis-(phenylene-4-), biphenylene-4,4'-, 3,3'-dimethoxy-biphenylene-4,4'-, 3,3'-diphenylbiphenylene-4,4'-, naphthalene-1,5- and tetrahydronaphthalene-1,5-diisocyanates and triphenylmethane triisocyanate; alkylene polyisocyanates such as ethylene, ethylidene, propylene-1,2-, butylene-1,4-, butylene-1,3-, hexylene-1,6-, decamethylene-1,10-, cyclohexylene-1,2-, cyclohexylene-1,4-, and methylene-bis-(cyclohexyl-4,4'-) diisocyanates. Phosgenation product of aniline-formaldehyde condensation may be used. Polyisothiocyanate, inorganic polyisothiocyanates, polyisocyanates which contain carbodiimide groups as described in German Pat. No. 1,092,007 and polyisocyanates which contain urethane groups, allophanate groups, isocyanurate groups, urea groups, imide groups or biuret groups may be used to produce the liquid isocyanate-terminated polyurethane prepolymers.